Neal S. Berke

Biodeterioration of concrete by the fungus Fusarium

The bacterial genus Thiobacillus is known for its ability to degrade concrete. A fungus was isolated from concrete samples and identified as a Fusarium species. Our data indicate that fungi also play an important role in the deterioration of concrete. We observed both weight loss and release of calcium when concrete was exposed to our isolate. Fungal degradation proceeded more rapidly than Thiobacillus-mediated degradation. Our study suggests that interaction between fungal metabolites and calcium in the concrete results in the formation of soluble calcium organic complexes.

Steel Corrosion in Concrete : Fundamentals and civil engineering practice

Introduction. Mechanisms of Steel Corrosion. Relations Between Corrosion and the Structure and Properties of Concrete. Corrosion Measurements. Corrosion Damage. Corrosion Measurements. Corrosion Control. Specificaitons and Design. Repair and Rehabilitation. Index.

Properties of high-performance concrete containing shrinkage-reducing admixture

The effects of a recently developed shrinkage-reducing admixture on high-performance concrete properties are described. High-performance concrete mixtures containing silica fume were cast with and without shrinkage-reducing admixture. The mechanical properties, drying shrinkage, and resistance to restrained shrinkage cracking were investigated. The results show that the shrinkage-reducing admixture effectively reduced the shrinkage of high-performance concrete, and resulted in a significant decrease in restrained shrinkage cracking.

Predicting long-term durability of steel reinforced concrete with calcium nitrite corrosion inhibitor

Abstract Steel reinforced concrete is one of the most durable and cost effective construction materials, but it can suffer in high chloride environments from corrosion due to chloride induced breakdown of the normal passive layer protecting the steel. One way of protecting embedded steel reinforcement from chloride induced corrosion is by the addition of corrosion inhibiting admixtures. The most widely used corrosion inhibiting admixture is calcium nitrite, due to its excellent inhibitor properties and its benign effect on concrete properties. One advantage to calcium nitrite is that its protection mechanism is well defined. In this paper data are presented that show the levels of chloride to which given levels of calcium nitrite will protect. Furthermore, it will be shown that once corrosion initiates, the rates are lower with calcium nitrite present. Finally, it is demonstrated how these results can be used by the design engineer in an integrated durability model to produce reinforced concrete structures with durabilities in excess of 50–100 years.

Corrosion of steel in cracked concrete

Abstract Corrosion of steel in concrete is studied typically in uncracked concrete. In the field, however, concrete often has cracks that extend to the reinforcing steel. Electrochemical corrosion ...

Comparison of Current Interruption and Electrochemical Impedance Techniques in the Determination of Corrosion Rates of Steel in Concrete

Steel reinforced concrete is a widely used construction material. It is often the material of choice in bridges, parking garages, and marine structures because of its good durability and resistance to corrosion. However, over time, even well designed concrete is susceptible to chloride intrusion from deicing or marine salts or both, resulting in corrosion of embedded steel. By the time corrosion of steel in concrete is readily noticeable, major repairs are often required. A nondestructive means of determining the corrosion rate of inaccessible steel is thus needed. Electrochemical techniques such as polarization resistance are useful, however resistivities of concrete range from 1000 to greater than 30 000 ohm-cm. Furthermore, reference electrodes are usually greater than 25 mm from the working electrode (rebars). Thus, large ohmic electrolyte resistance is present, even at the low current densities associated with steel in concrete, and must be accounted for to accurately measure corrosion rates. In this paper we compare the use of current interruption correction for ohmic resistance to an electrochemical impedance measurement at 20 KHz. In general, we find a good correlation between the two techniques, and demonstrate that substantial ohmic resistances are present.

Corrosion Activity of Steel in Cementitious Controlled Low-Strength Materials vs. That in Soil

Controlled Low-Strength Materials (CLSM) are high performance fills produced and delivered by ready mix suppliers. CLSM places faster than conventional compacted fill, requires less jobsite equipment, increases jobsite safety, and minimizes future settlement problems. Consequently, the use of CLSM as backfill material is a very attractive option. However, there are numerous factors that influence soil corrosion on buried structures, such as the electrical resistivity of the backfill material along with its pH and drainage characteristics. Corrosion experiments in which steel coupons were placed in simulated soil or covered with cement-based CLSM then placed in simulated soil are discussed.

Predicting times to corrosion from field and laboratory chloride data

Corrosion of steel in concrete is one of the major causes of the premature failure of steel reinforced concrete. In marine and deicing salt environments the ingress of chloride is the primary cause for the breakdown of passivity and the onset of severe corrosion. In this paper, we show how to develop effective diffusion coefficients for chloride ingress based on chloride profiles from several marine structures. Predictions of the times to reach chloride levels associated with initiation of severe corrosion are made. Chloride profiles using effective diffusion coefficients determined in other studies are given for bridge decks and parking structures. There are significant benefits of increased concrete cover and the use of corrosion inhibitors in increasing the time to corrosion. Finally, comparisons of Standard Test Method for Electrical Indication of Concretes Ability to Resist Chloride Ion Penetration (ASTM C 1202) coulomb values with effective diffusion coefficients, determined from field and laboratory studies, indicate that effective diffusion coefficients for low permeability concretes can be estimated using simple modifications of this test method. Thus, we demonstrate that knowledge of the chloride profile is useful to assess the future performance of existing structures that are not undergoing active corrosion, and in predicting the time to corrosion initiation of new structures.

Reply to Discussion: Corrosion of Steel in Cracked Concrete

Abstract This work replies to a discussion by D.B. McDonald of “Corrosion of Steel in Cracked Concrete,” which was published in Corrosion 50, 6 (1994): pp. 419–421. The original work by N.S. Berke,...

Hydrophobic concrete admixture product testing and validation : contractor's supplemental report for CPC Project F09-AR05A

The Department of Defense spends many millions of dollars annually to repair or replace steel-reinforced structures that are seriously damaged by corrosion. Reinforced concrete is readily damaged by corrosion because the cement/aggregate matrix is porous, allowing corrosive chemicals (e.g., chlorides from marine salts or road-deicing salts) to deeply penetrate structures following wetting/drying cycles. Damage modes include loss of reinforcement steel mass through corrosion and fracturing due to corrosion-product buildup or freeze/thaw cycling. These stresses can destroy a concrete structure many years short of its intended service life. This report documents one of several studies performed or supervised by the U.S. Army Engineer Research and Development Center to demonstrate or test the efficacy of a commercial hydrophobic concrete admixture in preventing the ingress of water and chlorides into reinforced concrete structures or specimens. Laboratory testing addressed chloride ingress threshold (destructive examination of specimens), absorption, and transport. This report includes an executive summary of the project and a detailed record of all testing program results. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR. ERDC/CERL CR-17-4 iii